ALTERNATIVE TO COMPRESSOR DEPENDENT AUTOMOTIVE AIR CONDITION SYSTEMS

Seth A. Bowman, Stafford C. Camp, Elizabeth A. Clarke, Nicholas M. Tate

ENGR 4020Fall Semester 2016

ALTERNATIVE TO COMPRESSOR DEPENDENT AUTOMOTIVE AIR CONDITION

SYSTEMS

Project Team: Seth A. Bowman,

Stafford C. Camp,

Elizabeth A. Clarke,

Nicholas M. Tate

Project Advisor: Dr. O. Hayden Griffin, Jr.

Company Sponsor: East Carolina University

Greenville, North Carolina 27858

Company Advisors: Dr. O. Hayden Griffin, Jr.

ENGR 4020

Fall Semester 2016

Department of Engineering

East Carolina University

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EXECUTIVE SUMMARY

Current automotive air condition systems are dependent on compressors that are powered by the engine, with additional components spread throughout the engine bay. Dr. O. Hayden Griffin desires a modern alternative to the current automotive air condition system. This modern alternative can provide benefit to individuals seeking to retrofit their vehicle with air conditioning and to automotive manufacturers seeking to develop new air conditioning solutions. Alternative designs were proposed and graded using technical feasibility, economic feasibility, and weighted decision matrices. Through this process thermoelectric cooling was identified as a viable design option. A test thermoelectric unit was procured and a test apparatus constructed. Through manufacturer data and test apparatus data, thermoelectric performance was quantified. For a comparison, a test vehicle was used to evaluate automotive compressor power consumption. Using mathematic analysis, a comparison between thermoelectric and compressor-driven air conditioning solutions was made. A prototype has been designed with the intent of retrofitting to vehicles without factory installed air condition systems, and is recommended for implementation. Data obtained in this project may be used to develop factory implemented thermoelectric air condition systems for future automotive applications.

KEYWORDS: thermoelectric, compressor, air conditioning, refrigerant, retrofit, automotive

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ACKNOWLEDGEMENTS

Dr. O. Hayden Griffin provided the initial inspiration for this project. Through his guidance this project has moved from a simple idea, to a more specific problem statement, to an implementable design. Dr. Griffin’s part in the project has been soft advice throughout with firm reinforcement when necessary. Because of his ongoing assistance this project has reached an appropriate solution and all group members have grown as engineers and team members.

Dr. Tarek Abdal-Salam provided additional expertise in the subject of thermoelectric systems. Through his personal research, he was able to provide practical examples of thermoelectric systems used in industry. In addition to his role as a subject matter expert, Dr. Salam facilitated funding through the University for the purchase of a test thermoelectric unit

Dr. Gene Dixon provided the group with valuable information on the necessary skill-set of a professional engineer. Through his lectures, writing, and individual conversations he has provided insight that can only be gained through experience. Additionally, he has provided the tools to create solutions rather than simply providing a pre-formed solution. He is an asset to the ECU Engineering department and the region it serves.

East Carolina University provided the funding and facilities to make this project possible. Through the test thermoelectric unit and the use of lab space, thermoelectric performance was made quantifiable. This information has proven to be a cornerstone piece to the final project design.

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Table of Contents

1. Introduction

1.1. Project Background

1.2. Current Situation

2. Problem Description

2.1. Problem Statement

2.2. Problem Definition

2.2.1. Scope of Work

2.2.2. Deliverables

2.2.3. Constraints

3. Engineering Design Specification

3.1. Introduction

3.2. Design Requirements

3.2.1. Functional Performance

3.2.2. Operating Environment

3.2.3. Human Factors

3.2.4. Economic

3.2.5. Geometric Limitations

3.2.6. Maintenance, Repair, and Retirement

3.2.7. Design Integrity

3.2.8. Safety

3.2.9. Pollution

3.2.10. Ease of Use

3.2.11. Appearance

3.2.12. Manufacturing

4. Current State of Air Condition Technology

4.1. Environmental Impact of Compressor Dependent Systems

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4.2. Power Consumption of Compressor Dependent Systems

5. Design Factors

6. Alternative Development

6.1. Ideation

6.2. Rating Proposed Alternatives

7. Thermoelectric Materials

7.1. Applying Thermoelectric Materials

8. Comparing Existing Systems to Thermoelectric Alternatives

8.1. Existing System Testing

8.2. Thermoelectric System Testing

8.3. Analysis of Testing

9. Design for Immediate Implementation

9.1. Maximizing Factory Component Utilization

9.2. System Components

9.2.1. Removing Heat from Cabin

9.2.2. Moving Heat Away

9.2.3. Expelling Heat from the System

9.3. System Design

9.3.1. The Thermoelectric

9.3.2. Plumbing and Fluid Movement

10. Technical Feasibility Analysis

11. Economic Feasibility Analysis

12. Conclusions

13. Recommendations

14. References

A. Appendix A – Reports from Testing A

A.1. Vehicle Testing A

A.2. Thermoelectric Testing A

B. Appendix B – Excerpts from Specification Sheets B

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B.1. Tellurex A22 Unit B

B.2. Tellurex SL1210 Unit B

C. Appendix C – Bill of Materials C

List of Figures

Figure 1.2.1 Conventional Clutch Cycling Orifice Tube Air Conditioning System

Figure 1.2.2 Air Condition Compressor Location Circled on GM LUV Engine

Figure 8.2.1 Test Box Design Overview

Figure 8.2.2 Thermoelectric Current Draw Over Time

Figure 9.1.1 Simplified Heater Box Layout

Figure 9.3.1.1 SL1210 Cold Plate

Figure 9.3.1.2 Mounting Block and Coolant Piping - Partially Exploded View

Figure 9.3.2.1 Ford Intercooler Coolant Pump

Figure 9.3.2.2 JOES Racing 45010 Expansion Tank

List of Tables

Table 6.1.1 Ideation Process Results

Table 6.2.1 Technical Feasibility Matrix of Proposed Alternatives

Table 6.2.2 Economic Feasibility Matrix of Technically Feasible Alternatives

Table 6.2.3 Weighted Decision Matrix

Table 8.1.1 Energy Cost of Air Condition System Use

Table 8.3.1 Calculation of Theoretical Power Consumption at Maximum Operating RPM

Table 8.3.2 Power Comparison Between Compressor and Thermoelectric

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Table 11.1 Thermoelectric Cooler Bill of Materials

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1. Introduction

1.1. Project Background

The motivation for a new automotive air conditioning design comes from the project’s sponsor, Dr. O. Hayden Griffin. Dr. Griffin is a Department Chair and Professor in the East Carolina University Engineering department. As a professor, Dr. Griffin is most interested in the mechanical engineering concentration and classes which apply to it. He is also interested in classic cars and their restoration and improvement.

Dr. Griffin expressed interest in an automotive air conditioning system which could utilize technological advances realized since the creation of the original automotive air conditioning configuration. Emphasis was to be placed on reducing the space that the system requires within the vehicle’s structure, reducing complexity, and reducing environmental impact. Dr. Griffin expressed specific interest in a system which could be easily retrofit to vehicles which were not originally fitted with air condition systems from the factory.

1.2. Current Situation

Current automotive air condition systems use an engine driven compressor, condenser, evaporator and often a drier. Along with these main components there are additional switches, control units, and sensors which control the overall function of the system and maintain safety. The compressor is typically located near the engine and the other pieces of the system are located throughout the engine bay. This system is difficult to access for servicing, takes considerable space within the vehicle’s structure, and uses an expensive refrigerant. The refrigerant used also contributes to global warming.

Air conditioning systems that use engine run compressors are mechanically complex. For this project, an air conditioning system is to be designed that functions without the use of an engine-driven compressor. Additionally, it will decrease environmental impact resulting from air conditioning. This environmental impact can be through construction, operation, or decommissioning. Finally, it will be compressor-less and fit into existing automobile structures.

Although the specific details of implementation may vary from one vehicle to another, the basic system remains the same. Current systems include an engine-driven compressor, a condenser, an expansion device, an evaporator, and an accumulator drier as shown in Figure 1.2.1 (MDH Motors, 2015).

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Figure 1.2.1 Conventional Clutch Cycling Orifice Tube Air Conditioning System

This project requires replacement of the compressor portion of the system shown in Figure 1.2.1, but other alterations to the existing system’s components may be made. With the compressor drawing energy from the engine, typically through a belt-driven pulley, it consumes energy and reduces available energy for transportation. Because most modern vehicles are powered through combustion, fuel economy is negatively affected. Figure 1.2.2 (next page) gives an example of a normal belt-driven compressor’s location on a modern engine (GM Authority, 2016).

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Figure 1.2.2 Air Condition Compressor Location Circled on GM LUV Engine

While the current system may only consist of five major components, each of these components often contain their own complex subassemblies. In the case of the air conditioning compressor, there is a subassembly of parts resembling a set of positive displacement pumps. The pumps are formed from arrays of two, four, or six cylinders, depending on compressor type. These pumps are subject to wear and subsequent efficiency decreases over time due to their mechanical nature. In addition to the pump array used within the compressor, there is also an electromagnetic clutch system which relies upon friction to activate and deactivate. Any time friction is introduced, another component of heat, and therefore wear, is introduced (Muscle Car Club, 2016).

With this current system, failures are most common within the compressor. The compressor is a sealed and non-serviceable unit, and for this reason repairs are frequently expensive. Component costs for automotive air conditioning compressor replacements can exceed $400 (Auto Parts Warehouse, 2016). This amount does not include added costs for labor and refrigerant fill.

The design for this project will focus on reducing the space and complexity of the current system. The new system will run independently from the engine as required by the sponsor. The sponsor expressed his interest in this kind of system because of the difficulty and cost that comes with replacing or installing a compressor, particularly on vehicles which weren’t originally fitted with air condition systems. Dr. Griffin also identified increased demand for vehicles with reduced emissions as possible applications for the technology. Both of these factors will be addressed in the new design. The new system will be compatible with all current cars including: older models, current

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models, electric cars, and hybrids. While current electric cars utilize electricity to power the air conditioning system, a compressor is still used.

The new design will be immediately applicable to vehicles lacking factory installed air condition systems. The current average cost of installing one of the most popular air condition system alternatives in a vehicle is around $1500 (Old Air Products, 2016). In addition to the $1500 cost of components, many individuals will require professional installation which will add an additional component of labor expense.

2. Problem Description

This project will create a modern alternative to current automotive air condition systems. The resulting alternative will be compatible with cars not currently fitted with air conditions systems and should be applicable to future automotive development.

2.1. Problem Statement

Current automotive air conditioners are complicated and occupy excess space within the car.

2.2. Problem Definition

Current automotive air condition systems are a burden on the car as well as the environment due to the compressor requiring direct engine power to operate, resulting in increased fuel consumption and emissions. In addition to the environmental burden caused be increased automotive emissions, the refrigerant used in the system has been shown to contribute to global warming. Finally, the current system is complex and requires discrete amounts of space within the vehicle. Because of the complexity and space requirement, adding an air condition system after the vehicle leaves the factory can be difficult. Exchanging the current air condition system model for a simplified non-compressor unit would lower automobile emissions, increase modularity, and potentially decrease costs.

2.2.1. Scope of Work

● Analyze current air condition systems● Develop alternatives● Build scale prototype of chosen alternative to validate assumptions● Conduct cost and thermal analysis of prototype● Create design proposal based on collected data

2.2.2. Deliverables

● Automotive air conditioning system design that is compact, minimizes environmental impact, and is scalable to existing and future vehicles

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2.2.3. Constraints

● Unit must be self-contained.

● Must not require the use of an engine-driven compressor.

● Must be able to accommodate flexible mounting locations for retrofit applications.

● Unit will ideally be equal or below the standard retrofit cost of $1500 for parts.

3. Engineering Design Specification

Title: Alternative to Compressor Dependent Automotive Air Condition Systems

3.1. Introduction

● Design Problem: Current automotive air conditioners are complicated and occupy excess

space within the vehicle.

● Intended Purpose: Design a new automotive air conditioner that reduces complexity and does

not use an engine run compressor.

3.2. Design Requirements

3.2.1. Functional Performance

● Decrease interior temperature of vehicle below ambient temperature.

3.2.2. Operating Environment

● Temperatures up to 300 if mounted within engine bay (Johnson R. J., 2004).℉● Temperatures as low as 14 if mounted within engine bay (Tetech, 2016).℉● Potential for vibration and shock.

● Power consumption limited to that which can be provided by on-board sources

3.2.3. Human Factors

● All moving parts self-contained within unit to mitigate hazards.

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3.2.4. Economic

● Should match or improve upon established market price of $1500 (Old Air Products, 2016).

● Cost to operate should be comparable to that of current systems, determined from fuel

consumption.

3.2.5. Geometric Limitations

● Should fit within geometric constraints of typical passenger vehicle.

● Maximum volume of 2 square feet for engine compartment install, 4 square feet for cargo

area install.

3.2.6. Maintenance, Repair, and Retirement

● Filter replacement intervals no less than typical OEM specification of 30,000 miles (Popely,

Rick, Cars.com, 2016).

● No less than 25% professionally replaceable/repairable parts.

● Minimum 75% of components able to be disposed of without special handling needs.

3.2.7. Design Integrity

● In the event of failure, no chance of injury to occupant.

● Electrical components specified to not exceed system capabilities.

● Fuses in place for all added electrical components.

3.2.8. Safety

● Correctly sized fuses for all electrical components and circuits.

● All components properly shielded to minimize damage caused by contact with other

components.

● No component positioned in a way that it might prevent vehicle control.

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3.2.9. Pollution

● Will not exceed current global warming potential of 1,430 for R-134a (United States

Environmental Protection Agency, 2012).

● Minimum 75% of components able to be recycled at end of service.

3.2.10. Ease of Use

● Industry standard control type, ie- fan speed, temperature, vent location.

3.2.11. Appearance

● Visually unobtrusive to occupants and drivers.

3.2.12. Manufacturing

● Minimum 50% of components available as off-the-shelf items.

● Service items such as fluids and fuses available from standard part house inventory.

4. Current State of Air Condition Technology

Current automotive air conditioning systems are thought to be as efficient as possible, and while they do effectively cool vehicles on hot days, they present other issues. The weaknesses present in the current automobile air conditioning design include, but are not limited to: the amount of energy needed to run the compressor, the environmental impact of the fluids used, and the scattered design of the current system’s elements. Because of this complexity, air condition systems must be deliberately engineered for each individual application.

4.1. Environmental Impact of Compressor Dependent Systems

Modern compressor-driven air conditioning systems use R-134a as a refrigerant due to its lower environmental impact in comparison to previously used refrigerants such as R-12 and other chlorofluorocarbons (commonly known as CFC’s or Freon). R-134a does still have an observable impact on climate change with a global warming potential (GWP) of 1,430. To put this value into perspective, methane has a GWP rating of 82, and R-11 (which is another CFC) has a GWP rating of 7020. While R-134a has a significantly lower rating than CFC’s, its impact is notable enough to warrant the proposed removal of systems which use it.

Due to growing environmental concern, the amount of electric and hybrid cars on the road is rising. Many environmentally-aware consumers are choosing these vehicles to decrease environmental

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impact due to emissions. Although decreasing emissions does greatly decrease environmental impact, further benefit can be realized with the elimination of refrigerants. In an attempt to reduce the environmental impact of newly built vehicles, the Environmental Protection Agency is looking for a refrigerant that will do less harm than the currently used R-134a. A possible solution has been found in the form of R-1234yf. As of 2015, about 25 companies worldwide are using the new R-1234yf refrigerant in their hybrid or electric cars, including the Toyota Prius and Tesla line of vehicles (Vehicle Service Pros, 2015).

R-1234yf refrigerant has a much lower global warming potential (GWP) than the currently used R-134a; the GWP of R-1234yf is only 4. This is a significant improvement over R-134a’s GWP of 1,430. R-1234yf has been deemed a more environmentally responsible solution, and the Environmental Protection Agency released a report in August of 2012 saying that it approves its use and expects it to be used by most companies by 2017. The reason for a slow transition comes down to the cost of R-1234yf. It is about ten times more expensive than R-134a and will require repair stations to purchase new equipment to service cars with the new refrigerant (Johnson A. , 2015). While the switch to a new refrigerant is being made slowly, a more economical solution is still needed.

4.2. Power Consumption of Compressor Dependent Systems

While the fluids used in compressors are a reason to promote removal, another drawback of modern compressors is the required power drawn from the motor. The extra amount of power required to run the compressor increases fuel usage and thus decreases fuel economy. This is bad both for the consumer who must spend more on fuel and for the environment as more fossil fuels are consumed. This fossil fuel consumption decreases global availability of a non-renewable resource and increases vehicle emissions.

Electric vehicles growth in popularity makes it necessary to also examine their air conditioning systems. Unlike traditional vehicles, electric cars have an electric drive motor that is unable to be connected to belts to drive a traditional compressor. For this reason, the air conditioning system must also be electric, and the systems in electric cars are modeled in consideration of this constraint. This system of air conditioning still uses a compressor, but it is one that has its own electric motor. This air conditioning configuration still reduces electric fuel economy equivalent (Weber, Bob, Auto Service Professional, 2011). This reduction is seen due to inefficiencies in converting electricity into mechanical energy. Even though electric cars are utilizing better refrigerants and less fossil fuel, there is still room for improvement when it comes to their air conditioning systems.

5. Design Factors

In determining design requirements for the project, shrinking the audience in terms of applicable automobiles is necessary. With all the different types of vehicles on the road, a target market was selected to constrain the design process. Mid-size cars were selected as the target vehicle type as they are the most popular. Mid-size cars have an interior cabin volume between 110 and 119 ft3.

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These cars are the most popular size sold in the US due to their versatility. Mid-size cars account for six of the ten bestselling vehicles of 2015 and were chosen for this reason. The bestselling mid-size car of 2015 was the Toyota Camry, due to its popularity it was used for evaluating the alternatives developed (Kelley Blue Book, 2015).

Along with this self-imposed design constraint, there are some requirements that will be common to all alternatives regardless of their specific design. All under hood mounted designs must be confined to a small space, about the size of a standard automotive heater box, estimated to be two cubic as stated in the EDS. If the design is to be placed exclusively in the cargo area, then overall volume may increase to four cubic feet. All designs must run independently of the engine and without the use of a compressor. The design must be easy to implement into multiple car types, implying that it must be as simple as possible.

The design should include packaging for the entire unit including subassemblies. The unit may need repair in the future, in which case consumers will ideally need to buy only the parts which need replacing. This design philosophy will increase value to the end consumer while minimizing environmental impact from needlessly discarded parts.

The current automotive air conditioning systems of midsize cars remove 18,000 BTUs of heat per hour (Harold Electric Company, 2016). This rate quantifies the amount of heat to be removed from the interior of the car per hour. This value will be an ideal target for a final design, with the understanding that current designs may not reach this value due to limits of existing technologies.

6. Alternative Development

Alternative solutions for automotive air conditioning were generated based upon established design criteria. Care was taken to create a design that can withstand the rigors of the automotive environment. Multiple alternatives were to be created to ensure a large pool of options. Once alternatives were proposed, they were evaluated to determine which would best fit the needs of the customer. The final design should ideally meet the cooling needs of the target volume while simultaneously fitting the allotted space and falling under energy consumption constraints.

Once an alternative is chosen, modeling software will be used to create a three-dimensional representation of the design. This will allow the design to be critiqued and altered easily before prototyping. A functional scale prototype will then be developed using parts similar to those which would be used on a production scale. The prototype will be used to validate assumptions of the designs capabilities and collect data to compare to the current air condition system model.

For the final design developed in this project, a bill of materials will be generated to predict final cost of production after adjusting for economies of scale. Once a per-unit price is established, market viability may then be assessed.

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Throughout the design process it is necessary to evaluate design alternatives against project constraints. After prototype finalization and economic analysis is performed, final conclusions will be drawn. Some conclusions drawn may include final effectiveness versus proposed effectiveness, final cost, and perceived adaptability of design to multiple vehicles. Additional applications of the technology will be explored with the intention of applying to other uses.

6.1. Ideation

The ideation process seeks to generate as many possible solutions or alternatives as possible. All group members proposed individual ideas, and further ideas were generated in a group setting. The purpose of ideation is not to rate or judge any idea, but simply to collect as many broad and varied proposals as possible. Ultimately, ten possible solutions were generated. Table 6.1.1 below shows the results along with a brief description.

Table 6.1.1 Ideation Process Results

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6.2. Rating Proposed Alternatives

Determining the technical feasibility of the alternatives involved analyzing each alternative to determine if it met all the Engineering Design Specifications. If it was determined that the alternative did not meet the Engineering Design Specifications, then possible changes to the alternative to make it feasible were considered. If no changes were possible to make the alternative feasible then the alternative was not considered to be a possible solution. From the ten alternatives listed in the technical feasibility matrix, four were deemed as feasible and thus possible solutions to the problem.

The Technical Feasibility Matrix is shown below in Table 6.2.1. Feasible alternatives are highlighted in blue for visibility.

Table 6.2.1 Technical Feasibility Matrix of Proposed Alternatives

Alternatives considered in the technical feasibility analysis were also considered for economic feasibility. An economic feasibility analysis was conducted in the same way as the technical feasibility excepting the criteria. For economic feasibility, the criteria for passing was based on the cost of the alternative taking into consideration the cost of implementation, maintenance and repair.

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Solutions eliminated in the technical feasibility matrix were no longer considered for the economic feasibility matrix. The economic feasibility matrix is shown in Table 6.2.2.

Table 6.2.2 Economic Feasibility Matrix of Technically Feasible Alternatives

As shown above, all technically feasible alternatives were also deemed economically feasible. The determination of their feasibility was based on comparison to the cost of the currently used method of automotive air conditioning. Although there were some alternatives which may have been economically feasible that were not considered, their exclusion was due to failure of the technical feasibility analysis.

The alternatives deemed feasible after both the economic and technical feasibility analyses were inserted into a weighted decision matrix to undergo further analysis. Four alternatives progressed to this phase of the decision-making process, they were: electric fans implemented around the interior of the car, thermoelectric devices that cool air using electric current, a battery run compressor using R-1234yf and an ammonia based system that uses ammonia and a boiler as opposed to a traditional refrigerant. These four alternatives were placed into the weighted decision matrix shown below in Table 6.2.3.

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Table 6.2.3 Weighted Decision Matrix

This matrix was created based on the attributes most important to the sponsor. The sponsor put an emphasis on keeping the unit as compact as possible, so the size of the alternative received the most weight at thirty percent. How well the alternative cools (effectiveness) and how often it works without fail (reliability) were the next highest weighted attributes, both receiving twenty percent. Ease of installation and power consumption received smaller weights at fifteen and ten percent respectively. Cost received the smallest weight, at five percent.

After the alternatives were scored for each attribute, the total score was calculated and the alternative with the highest score was the thermoelectric device with a score of 6.25, the runner up was the battery run compressor with a score of 5.65. The thermoelectric was chosen as the best solution among the proposed alternatives and was the focus of research, design, and testing.

7. Thermoelectric Materials

As the chosen design alternative, thermoelectric materials and their function are central to a design solution. Although their use is not uncommon in other industries, thermoelectric cooling has not yet been applied to automotive cooling on any large scale. Thermoelectricity is produced when a conversion occurs at a solid-state between thermal and electrical energy. Thermoelectric function is described by three principles: the Peltier effect, the Seebeck effect and the Thomson effect.

The Peltier effect is the most prominent governing principle of the three and was discovered in 1834 by Jean C.A. Peltier. This effect states that when current passes through a circuit of two dissimilar materials, one end generates heat and the other releases it. When this happens, heat energy is moved from one conductor to the other. This heat transfer results in a distinct “hot” and “cold” side to the

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thermoelectric material. By reversing the polarity of the electric current, the heat flow reverses direction. This process is reversible and linearly dependent, meaning it can be scaled up. The dissimilar materials used for thermoelectrics are typically bismuth telluride and copper but some companies use proprietary materials (Tellurex Corporation, 2016).

The Seebeck effect was discovered before the Peltier effect by Thomas J. Seebeck. The Seebeck effect states that when a loop of two dissimilar materials are heated on one side, an electromagnetic field is generated. Seebeck noticed that the strength of this field changed in proportion to the temperature difference. The Seebeck coefficient, represented by S in Equation 1, shows the relationship of the temperature difference and voltage to the magnitude of the electromagnetic field generated.

S=−∆ V∆ T

(1)

Because of the Seebeck and Peltier effect, thermoelectrics can be used in two ways. They can use heating or cooling to create electric current as well as use electric current to create heating or cooling. This describes the two main applications of thermoelectric materials, thermoelectric cooling plates and thermoelectric generators. The Seebeck coefficient does not allow for a constant generation of power because the temperature difference will always be changing, as will the magnitude of the electromagnetic field.

The Thomson effect corrects the varying power generation problem faced by the Seebeck effect. This effect states that passing a current through the gradient created by the changing temperature difference will result in a continuous Peltier effect. The Thomas effect makes it possible to predict heat rate generation using the following equation, Equation 2.

q̇=−KJ ∆ T

(2)

Where J is the current density, ∆ T is the temperature gradient and K is the Thomson coefficient. Finally, this is related to the Seebeck coefficient below in Equation 3 (Madre, 2016).

K=T dsdT

(3)

The existence of the Peltier effect has been known for some time, but practical applications of it are recent. There are several companies that manufacture thermoelectric plates but few consumer

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products utilize this technology. Some recently released thermoelectric products include computer casings, refrigerators and home air conditioners.

7.1. Applying Thermoelectric Materials

Although not new, thermoelectric technology is still developing. Most of the current applications for it are involved with cooling relatively small volumes. Applying thermoelectric technology to automotive cooling is not an application that has been previously researched and it may be found to be unrealistic through further testing. To test the technology, its principles must first be understood.

To test the possibilities and limitations of current thermoelectric technologies, a thermoelectric cooling unit was obtained from the Tellurex Corporation. The unit they provide includes a plate which houses the thermoelectric materials, two fans which act as the heat sinks, and controller which allows the temperature to be monitored and set. This unit was used in testing to determine if the thermoelectric is a feasible option for replacing compressor driven air conditioning in automobiles. Manufacturer provided technical specifications can be found in Appendix B.

8. Comparing Existing Systems to Thermoelectric Alternatives

In comparing the performance of compressor-driven air condition system with thermoelectric performance, it is necessary to standardize the units being compared wherever possible. To quantify both systems power consumption in like terms, the Watt was chosen as the desired power unit. Through the manufacturer provided data sheet, which is verified experimentally, the power consumption of the test thermoelectric unit can be ascertained.

Like the experimental testing performed on the thermoelectric unit, experimental data can be acquired from a test car. Because engine driven compressors do not take their power directly from electricity, some unit conversion is required. In the case of this comparison, fuel consumption is related to power content and then compared to data obtained from thermoelectric testing.

8.1. Existing System Testing

To generate a base for comparison, power data was collected from a test vehicle and compressor. The vehicle chosen was a 2012 Chevrolet Sonic with a 1.4-liter gasoline engine. This vehicle was chosen because it represents a modern mid-size car with a traditional compressor based air condition system. To collect data, hardware and software from HPTuners were used. With this software, engine parameters could be monitored with a 100-hertz sampling rate.

Two steady state usage cases were tested, and in both cases a control test was performed to compare to test results. This method gave four bodies of sample data from which to collect information. Ultimately, the fuel consumption increase for compressor use was determined at both idle and highway operating speeds. This data allowed the equivalent power consumption to be calculated. Table 8.1.1 gives an example of the calculations performed.

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Table 8.1.1 Energy Cost of Air Condition System Use

The result was an energy consumption increase of 5.05 kW at idle speed, and an increase of 7.81 kW at highway speed. This value is representative of the total cost to operate the compressor, and accounts for inefficiencies present in the engine, belt system, and compressor itself. Detailed lab report data can be seen in Appendix A.1.

8.2. Thermoelectric System Testing

For the thermoelectric test, a test box was developed using a small sized thermoelectric that could be used to cool the boxes interior volume. The test box developed for this project was designed with the intent to measure cooling performance while also keeping track of power consumption. The thermoelectric unit used for this test box was a Tellurex A22 Thermoelectric Air-to-Air cooler manufactured by the Tellurex Corporation. The size of the unit is scaled to cool small volumes such as in medical refrigeration.

The Air-to-Air unit was accompanied with a power supply and controller also manufactured by Tellurex. These three components are manufactured to provide a “plug-and-play” system for easy installation into an apparatus. The three components were designed to sit on the lid of a plastic container where a hole was cut for the thermoelectric unit to occupy a portion of the interior of the box. The interior of the box was lined with half-inch insulating foam material with an R-value of 2.4 to keep the cool air from warming due to the outside environment. Figure 8.2.1 illustrates the basic design of the test box.

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Figure 8.2.1 Test Box Design Overview

To operate the test box, the power supply was provided 110-volt AC power. When powered, the thermoelectric plate and accompanying fans move air through the fins attached to the plate. During normal operation, current to the thermoelectric is regulated by the control unit. This control system uses temperature data collected from a thermistor installed within the box to maintain a steady temperature.

For testing the thermoelectrics max power consumption, the controller was removed from the system. This change was made to have the plate run at max cooling capacity. During testing the voltage input to the thermoelectric was held steady at 12 volts to simulate standard automotive voltage levels. Figure 8.2.2 shows thermoelectric current draw over a span of three minutes.

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Figure 8.2.2 Thermoelectric Current Draw Over Time

The data from box testing indicates that the thermoelectric has a peak power consumption of just

below 50 watts, and the two installed fans have a power consumption of 5 watts each. This brings

total power consumption of the test unit to 60 watts. Complete test details and results can be found in

Appendix A.2.

8.3. Analysis of Testing

The collected test data is used along with thermoelectric data sheets provided by the manufacturer and standard air condition values obtained through research. These values can be used to compare the existing air condition system to the potential capabilities of a thermoelectric. Existing air condition systems can be expected to ideally remove 18,000 BTU of heat per hour (Harold Electric Company, 2016). In comparison, the A22 unit tested is rated to remove 75 BTU of heat per hour (Tellurex Corporation, 2016).

Through testing, the existing air condition system was found to consume power differently depending on operating rpm. With an idle speed of 780 rpm, power consumption was steady at 5046 watts. At a constant speed of 60 miles per hour, engine rpm was increased to 1860 and the compressor required 7806 watts of power to operate. Because the car’s gear ratio is fixed, engine

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speed for a desired vehicle speed can be calculated. Using this calculated engine speed, linear interpolation can be used to calculate maximum power consumption by the air condition compressor. Table 8.3.1 below shows the Excel calculation used for this.

Table 8.3.1 Calculation of Theoretical Power Consumption at Maximum Operating RPM

A theoretical vehicle speed of 80 miles per hour was chosen to mirror the maximum posted speed limit of 70 miles per hour with an additional 10 miles per hour added for safety. At this speed, compressor power consumption is calculated to be 9390 watts.

Experimentally the A22 thermoelectric unit had a maximum power consumption of 60 watts. This value is in line with the manufacturer specified maximum power consumption of 72 watts (Tellurex Corporation, 2016). To properly account for all cases, the manufacturer specified power consumption will be used for calculations.

With the power consumption of the compressor and the thermoelectric both standardized to the same unit of power, the power source must then be considered. Due to the nature of the experiment, the overall power consumption of the compressor already accounts for inefficiencies within the engine, drive system, and compressor itself. A direct relationship between fuel consumption and air condition use is demonstrated.

In the case of the thermoelectric, electric power consumption is quantified, but the power needed to generate this level of electrical power is not. In a modern vehicle, electrical power can come from many sources, but the most common by far is the engine’s alternator. The alternator converts the engine’s mechanical energy, which was created through fuel consumption, to electrical energy. Considering efficiency levels of the engine, belt system, and alternator itself, overall efficiency in energy conversion from gasoline to electric is commonly 21% (Bradfield, 2016).

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With the collected data, a like for like comparison is made between the compressor and thermoelectric. The comparison assumes that energy requirements in the form of fuel consumption will be held equal between the compressor and thermoelectric. When this assumption is made, the ideal cooling capability of the thermoelectric can be seen. Because the most likely source of electrical energy is the alternator, a 21% conversion efficiency is assumed. An ideal 100% efficiency is also calculated in the event that an alternative energy source is available. Excel is again used for calculations, and the results can be seen below in Table 8.3.2.

Table 8.3.2 Power Comparison Between Compressor and Thermoelectric

As shown, the efficiency and performance of compressor based systems have been optimized over its many years of use. With the thermoelectric being a relatively new technology and the minimal amount spent on research and development by comparison, it falls behind in efficiency. Even with this consideration, the cooling capabilities of the thermoelectric still have merit in the automotive world.

While existing factory-installed air condition systems can remove 18,000 BTU per hour at maximum duty under ideal conditions, they are rarely used at a fraction of this level. Although the raw cooling performance of an equivalent thermoelectric is only 11% of the compressor system, this does not mean the perceived performance will be diminished to this degree. The compromise will be felt most during extremely high temperatures, but will be noticed less when ambient temperature needs to be decreased by only five to ten degrees.

9. Design for Immediate Implementation

Although the cooling performance in relation to power consumption of existing thermoelectric devices is one of the main concerns to a successful implementation, the more immediate constraint is space. Although it was determined that a thermoelectric unit equal to 27 test units would be at or below the power consumption of the compressor, fitting these units would be difficult or impossible without major modifications and per-vehicle designs.

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With the engineering design specification and Dr. Griffin’s requirements in mind, a design was created that would focus primarily on the problem of adding an air condition system to those vehicles which were not factory equipped with a compressor based system. By focusing on this group, comparison to existing compressor based systems is greatly minimized. The modest level of cooling provided by a thermoelectric is a large improvement over no air condition system at all.

9.1. Maximizing Factory Component Utilization

To maximize the benefit realized by the final design, it is desirable to repurpose as many factory components as possible. Through this design philosophy, component costs can be minimized, and installation becomes less invasive to the vehicle. Because the install is less invasive, the skill level required to install is also decreased. A system which can be installed by the end user decreases labor costs associated with professional install.

Almost all cars, even those without air condition systems, are equipped with factory heat. Engine coolant which has been warmed by the running engine is circulated through a “heater core” within the heater box. The heater core is similar to a car’s radiator, and when cooler air passes through it the air is warmed by the heat of the engine coolant. Figure 9.1.1 below provides a simplified representation of a typical heater box (Stepnicka, 2016).

Figure 9.1.1 Simplified Heater Box Layout

The evaporator shown in Figure 9.1.1 would not be present in a vehicle without an air condition system, but all other components are usable. The heater core and blower motor will be repurposed for the thermoelectric retrofit, as will their factory installed wiring and controls.

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9.2. System Components

At its most simple level, an air condition system removed heat from one area and expels it in another. By removing heat more quickly than it is reintroduced, the temperature of the desired area is decreased. The thermoelectric design will operate using this principle.

9.2.1. Removing Heat from Cabin

In its standard configuration, the vehicle’s heater core is used to introduce heat in to the cabin. For the thermoelectric cooling retrofit, the heater core will be repurposed to remove heat. Fluid flowing through the heater core will be at a lower energy than cabin temperature. The factory blower motor will circulate the warmer air through the repurposed heater core. As the warmer air is forced through, energy in the form of heat will flow from the air into the heater core and its fluid.

As energy and heat are removed from the cabin by using this method, cabin temperature will be decreased. It will also allow the system to produce the “cool air” that is characteristic of a typical air condition system.

9.2.2. Moving Heat Away

As the heater core and fluid collect energy from the cabin air, this energy must be moved out of the heater core to keep it at a lower relative temperature. An ideal medium for this heat transfer is water. Because the application may be exposed to below freezing temperatures, it is recommended that a blend of antifreeze and water be used, similar in ratio to that found in the engine cooling system.

To circulate the cooling fluid, an electric water pump will be used. Electric water pumps are often used for automotive heat exchangers, typically mounted within the engine bay for supercharged engine applications. These water pumps are ideally suited for the intended environment of this system.

9.2.3. Expelling Heat from the System

Because the goal of the system is to cool the cabin below ambient temperature, passive cooling alone is not adequate. A thermoelectric array will be used to remove heat from the cooling fluid and expel it to the outside environment. By using the thermoelectric to cool the fluid rather than the air directly within the cabin, flexibility in mounting is increased.

In addition to an increase in mounting flexibility, array size is also customizable. Thermoelectric array can be used in parallel or series arrangement to maximize heat removal from the cooling fluid. By extension, cooling capability of the system will be increased.

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9.3. System Design

Heater core inlet and outlet size can vary from one vehicle to another, but ¾” is the most common size. For this reason, the design of the system is built around ¾” hose size. In the event of a non-standard hose size at the outlet of the heater core, adapter fitting can be easily sourced. For power, any car with a standard 12-volt direct current charging system should be adequate. A complete bill of materials including source, quantity, and pricing can be found in Appendix C

9.3.1. The Thermoelectric

For testing, Tellurex’s A22 air to air model was used. For the retrofit application, Tellurex’s SL1210 model is chosen. Specification sheets for this model are provided in Appendix B.2. Each SL1210 unit consumes 120 watts of power with a heat rejection of 170 BTU per hour. Figure 9.3.1.1 (next page) shows the SL1210 cold plate model (Tellurex Corporation, 2016).

Figure 9.3.1.1 SL1210 Cold Plate

Although a minimum quantity of one unit may be used, an array of two to four is recommended. For mounting flexibility, the proposed unit is two units mounted in series, with the option to add another two-unit array later.

The thermoelectric units are mounted to an aluminum block for stability and to promote heat transfer from the cooling fluid through conduction. The outer surface of the aluminum mounting block is

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insulated to minimize ambient heat transfer in to the aluminum cooling block. Figure 9.3.1.2 (next page) shows the aluminum mounting block with cooling fluid pipe in place.

Figure 9.3.1.2 Mounting Block and Coolant Piping - Partially Exploded View

This block, and the associated piping, are the only component for the system that will not be available “off the shelf”. Both components are expected to exceed the life of the vehicle. As a result, the customer should not need to replace them after initial purchase.

9.3.2. Plumbing and Fluid Movement

By using the standard ¾ inch plumbing size, options for components become easier to source. After the thermoelectric, the most integral part to the system is the electric water pump. For this task, a unit from Ford was chosen. The M-8501-MSVT intercooler coolant circulation pump is designed with its own mounting bracket and ¾ inch inlet and outlet barb fittings. Figure 9.3.2.1 shows an image of the pump (Summit Racing, 2016)

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Figure 9.3.2.1 Ford Intercooler Coolant Pump

With pumping needs satisfied, the next concern becomes filling and servicing the system. Because this will not be a high-pressure system, a standard aluminum tank is acceptable. For this purpose, the JOES Racing Products 45010 expansion tank was chosen. The tank has a one quart capacity and NPT threaded inlet and outlet to accommodate the ¾ inch hose used for plumbing the system. The expansion tank is shown below in Figure 9.3.2.2 (Summit Racing, 2016).

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Figure 9.3.2.2 JOES Racing 45010 Expansion Tank

In addition to the two main components of the pump and expansion tank, various plumbing fittings will be required. There are many hose options, but for a basic kit a bulk rubber hose will be sufficient. A detailed bill of materials is located in Appendix C

10. Technical Feasibility Analysis

The proposed solution of a thermoelectric system to provide automotive cooling fits many of the basic criteria and constraints provided in the engineering design specification. Most notably, it should provide some level of cooling to occupants, fit within vehicle space constraints, and be implementable at a price below that of other systems.

Because of size, cost, and budget constraints, performance will not be comparable to that seen with a compressor driven system. For this reason, the system should only be considered for vehicles without a factory equipped air condition system.

11. Economic Feasibility Analysis

The economic impact of the proposed alternative was analyzed as part of determining its practicality. Since the Thermoelectric system will be installed in a car with no previous air conditioning system, all parts will need to be purchased to implement the system. A bill of materials was devised with prices and quantities for each item. Table 11.1 below shows the bill of materials for the proposed thermoelectric air condition system.

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Table 11.1 Thermoelectric Cooler Bill of Materials

The total cost of parts comes is estimated to be $988.85. This value is within the $1500 limit specified by the Engineering Design Specification. Labor cost to install the system will vary based on vehicle, location, and owner’s skill level. If professional installation is required, labor rates vary from $60 to $100 per hour (IAC Publishing, 2016). Because of the kits relative simplicity, installation time may be as low as two to four hours. By comparison, other aftermarket air conditions systems can take a minimum of eight hours to install.

Along with the initial cost of parts, cost to operate can be a factor in deciding to purchase or not. When compared to a standard compressor driven air condition system, the proposed thermoelectric system uses less than 4% of the required power. Even with the inefficiencies present in existing alternator technology, fuel consumption of the thermoelectric would only be 20% of that seem by the compressor.

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12. Conclusions

Current automotive air conditioners are complicated and occupy excess space within the car. While the system performs reasonably, it is also environmentally unsound and expensive in terms of maintenance and repair. The leading component of the system is the engine-driven compressor that utilizes refrigerants such as R134a while also drawing horsepower from the engine to operate. The standard air condition system in an automobile is designed to remove around 18000 BTU’S’s of heat from the cabin.

The purpose of this project was to use ideation, various analyses, and specified criterion to formulate a proper alternative design to replace the current automotive air condition system. Alternatives were chosen to replace the current system and analyzed technically and economically. The alternatives that were found feasible were then compared using a weighted method to choose a single best alternative based on criteria such as cost, power consumption, and ease of installation. The decided alternative uses thermoelectric technology to remove heat from the cabin of the vehicle. The basic concept of thermoelectrics is that when current is provided to the plate, heat is drawn from one side of the plate and transferred to the other. A scale model of the proposed design was created and tested to compare to the performance of the current implemented system. A second test was conducted on a selected car to find values to compare to the test box when properly scaled.

From the vehicle, it was found that the current air condition system uses between 5046 and 7806 watts of power based on operating speed. The test of the thermoelectric box concluded that the plate used 50 watts of power to remove 75 BTU’S’s of heat. This value was then scaled up to theoretically compare to the car air conditioner. When compared, the thermoelectric was theorized to perform at a value of around 9700 BTU’S’s of heat removal for equal power consumption. This performance equals approximately 50% of the currently implemented technology.

The largest problems found with thermoelectrics were the size and power consumption. While the power and performance of the thermoelectric can compare to an engine-run compressor when scaled, the required size and power needs greatly exceeds the limitations of installation within current mid-sized cars. As the technology matures, it is possible the efficiency and size of the units will improve, making the thermoelectric a more attractive solution.

13. Recommendations

Based on current technology it is recommended that the sponsor install the proposed thermoelectric system described. The findings of this project show that while a thermoelectric air condition system cannot match a compressor driven system in cooling power, it can provide some cooling at a lower price than market alternatives.

Due to the comparatively large space and powers need of the thermoelectric material, it is infeasible to completely replace the compressor driven systems that already exist in modern cars. If thermoelectric material can improve in efficiency and size, it is possible that future vehicles can use

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the technology from the factory. Investment by OEM manufacturers can help speed the maturation of the technology and bring it to reality more quickly.

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14. References

American Society of Mechanical Engineers. (2016, October 17). P157_Ethics. Retrieved from ASME.org:

https://www.asme.org/getmedia/9EB36017-FA98-477E-8A73-77B04B36D410/P157_Ethics.aspx

Auto Parts Warehouse. (2016, February 19). APW Parts Finder. A/C Compressor.

Greene, R. (2016, October 17). Be Like Henry Ford: Apprentic Yourself In Failure. Retrieved from Fast

Company: https://www.fastcompany.com/3002809/be-henry-ford-apprentice-yourself-failure

Harold Electric Company. (2016, February 17). Compressor Section. Compressor Section.

Johnson, A. (2015, May 11). 2015 Refrigerant Price Per Pound Predictions. Retrieved March 4, 2016

Johnson, R. J. (2004). The Changing Automotive Environment: High-Temperature Electronics. IEEE

Transactions on Electronics Packaging Manufacturing IEEE Trans. Electron. Packag. Manufact., 164-

76.

Kelley Blue Book. (2015, July 29). 10 Best-Selling Cars of 2015. Retrieved March 29, 2016

MDH Motors. (2015). A Typical Orifice Tube Equipped Air Conditioning System. Retrieved February 22, 2016,

from A/C System Operation.

Muscle Car Club. (2016). Air Conditioning and Heating Systems. Retrieved March 13, 2016

Old Air Products. (2016, February 29). Old Air Products A/C Systems and Parts.

Popely, Rick, Cars.com. (2016, January 24). How Often Should You Change the Engine Air Filter? Retrieved

April 5, 2016

statista. (2016, October 17). U.S. Market Share of Automobile Industry. Retrieved from statista: The statistics

portal: https://www.statista.com/statistics/249375/us-market-share-of-selected-automobile-

manufacturers/

Tellurex Corporation. (2016). Single Stage Thermoelectric Cooling Modules. Retrieved April 20, 2016, from

Tellurex.com: https://tellurex.com/products/single-stage-thermoelectric-cooling-modules/

Top Achievement. (2016, October 17). Creating S.M.A.R.T. Goals. Retrieved from Top Achievement: Self

Improvement and Personal Development Community: http://topachievement.com/smart.html

United States Environmental Protection Agency. (2010, October). Transitioning to Low-GWP Alternatives in

MVAC’s. Retrieved April 5, 2016

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United States Environmental Protection Agency. (2012, August). 2017 and Later Model Year Light-Duty

Vehicle Greenhouse Gas Emissions and Corporate Average Fuel Economy Standards: EPA Response to

Comments. Retrieved February 22, 2016

Vehicle Service Pros. (2015, March 19). Current List of OE's That Use R-1234yf Refrigerant. Retrieved March

4, 2016

Weber, Bob, Auto Service Professional. (2011, June 16). Electronic Air Conditioning. Retrieved February 12,

2016

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A. Appendix A – Reports from Testing

A.1. Vehicle Testing

ABSTRACT

The purpose of this experiment is to gain empirical data on the fuel consumption characteristics of modern automotive air conditioning systems. Through the collected data and with the use of reference material it is possible to equate fuel consumed to a value of power. Using VCM Scanner software, operating parameters from the test vehicle, a 2012 Chevrolet Sonic LTZ, were collected. Engine speed, coolant temperature, vehicle speed, instantaneous fuel flow, intake air temperature, and ethanol fuel percent data were collected. In total, four three minute tests were performed. Of the four tests, data was collected at idle speed and steady state driving for all test parameters. By aggregating the data and using established conversion factors, air conditioning energy consumption at idle and steady cruising speeds were found to be 5.05kW and 7.81kW, respectively. Using these calculated amounts, it is possible to equate energy consumption between various power sources and air conditioning types.

INTRODUCTION

The purpose of this experiment is to collect data from a test vehicle to calculate power consumed by modern compressor based automotive air conditioning systems. Due to hardware and software limitations, it is not possible to directly sample power consumption. Available data must be used to calculate the desired information. With the sampling of engine speed, coolant temperature, vehicle speed, instantaneous fuel flow, intake air temperature, and ethanol fuel percent data it is possible to calculate power consumption.

Because of modern blended fuel sources, the first calculation made is that of fuel density. Fuel density calculation is based on sample data from the ethanol sensor and then compared to tabulated densities for standard gasoline and ethanol. The fuel density formula is shown in Equation 1.

Df =e∗(De)+(1−e )(Dg) (1)

Where Df is total fuel density in pounds per gallon, e is ethanol fuel percent, De is tabulated ethanol density in pounds per gallon, and D g is tabulated gasoline density in pounds per gallon. With fuel density information calculated, experimental values for fuel flow in pounds per hour can be used to estimate fuel consumption. Equation 2 shows the formula for fuel consumption.

C= FDf

(2)

Where C is fuel consumption in gallons per hour, F is experimental flow rate in pounds per hour, and Df is fuel density in pounds per gallon. Again, using tabulated values, it is possible to calculate energy density of the fuel used during the test. The formula for fuel energy density is shown below in Equation 3.

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E=e∗( Ee)+(1−e)( Eg) (3)

Where E is fuel energy density in kilowatt hour per gallon, e is ethanol fuel percent, Ee is ethanol energy density in kilowatt hour per gallon, and Eg is gasoline energy density in kilowatt hour per gallon. Finally, power consumption can be calculated with data and calculated values. The formula for power consumption is shown in Equation 4.

P=E∗C (4)

Where P is power in kilowatts. E and C are values for fuel consumption and energy density from equations two and three above.

PROCEDURE

The procedure involves collecting data experimentally from a test vehicle and interpreting the data using known conversion factors. For this test the chosen test vehicle is a 2012 Chevrolet Sonic LTZ. The test vehicle uses a 1.4-liter turbocharged engine with a fuel blend of ethanol and gasoline. Software used for the test is VCM Scanner. This software is created by HPTuners and uses their OBD2 dongle for data acquisition from the vehicle’s factory engine control module. Collected data is exported to Microsoft Excel for analysis.

The VCM Scanner software is configured to collect data relevant to this test. In this case engine rpm, instantaneous fuel flow, AC clutch position, engine coolant temperature, vehicle speed, intake air temperature, and ethanol fuel percent. Engine RPM, AC clutch position, engine coolant temperature, vehicle speed, and intake air temperature are logged only to validate assumptions made in each step of testing. Instantaneous fuel flow and ethanol fuel percent are the only values relevant to the desired results.

With the software set up and the test vehicle at operating temperature, it is possible to perform the first of four tests. The first two tests sample fuel flow at idle engine speed. For the first test, the air condition system is off. The car is allowed to idle for three minutes while data is collected, then the data is saved and exported to Excel. Figure 1 below shows an example of the VCM Scanner software during testing.

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Figure 1 The VCM Scanner Testing Screen

After the first test is complete, the second test is conducted in the same way, with the only difference being the air conditioner status. The car is allowed to idle with full air conditioning demand for three minutes while data is collected.

The final two tests are conducted at 60 miles per hour. The driven route has no discernable elevation change and a posted speed limit of 60 miles per hour. The test route is driven at 60 miles per hour with air condition off for three minutes while data is collected. The test route is then driven again with air condition on to complete the final test.

RESULTS

With the data from the four tests exported in Excel, the first step is to average each column of results. Along with the average values, minimum and maximum values are taken. By using these three values it can be verified that measurements were made during steady state conditions.

When all four tests are shown to be steady state, relevant information is exported to a separate sheet in Excel. This is done to minimize clutter and to aggregate data from the four tests.

Relevant data from the tests is ethanol fuel percent and instantaneous fuel flow. Ethanol fuel percent data is used to calculate fuel density and fuel energy density using Equations 1 and 3, respectively. Example calculations taken from test one are shown below; test one has an ethanol fuel value of 78.43%.

Df =e∗(De)+(1−e )(Dg)

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Df =.7843∗(6.590)+(1−.7843)(6.073)

Df =6.478 lbgal

E=e∗( Ee)+(1−e)( Eg)

E=.7843∗(21.3)+(1−.7843)(33.2)

E=23.87 kWhrgal

Because instantaneous fuel consumption data is delivered as pounds per hour, it is necessary to convert to gallons per hour. For this calculation, Equation 2 is used, again with test one as an example with a fuel consumption of 1.771 pounds per hour.

C= FDf

C=1.7716.478

C=0.273 galhr

Finally, with a known fuel consumption rate and fuel energy density, energy consumption can be calculated using Equation 4.P=E∗C

P=23.87∗0.273

P=6.522kW

This value represents the total energy consumption for the whole car when gasoline is the power source. These calculations can be repeated for test two, three, and four to make comparison between air condition off and on states.

Table 1 below shows results for all four tests as well as difference in value between states. This difference can be attributed to air conditioner compressor power requirements.

Table 1 Test data along with calculations

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The test data shows a clear correlation between energy consumption and air conditioner status. Energy cost is minimized at idle because of the slower engine speed. As engine speed increases, so does energy consumed by the compressor. This is because the compressor is turned at a fixed rate that varies along with engine speed.

CONCLUSION

The purpose of this experiment was to show the energy consumption from the use of air conditioning. As the data shows, there is a non-negligible increase in energy consumption when the air conditioning system is on. This data can be used to better compare the cost of other air conditioning strategies and energy sources.

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A.2. Thermoelectric Testing

ABSTRACT

The purpose of this experiment was to determine the amount of power the thermoelectric prototype used at maximum cooling capacity. These results will be analyzed and compared to the amount of power an air conditioning system in an automobile uses. The amount of power an automotive air conditioning system uses is much more than the thermoelectric prototype and will need to scale the prototype to the same amount of power to find if it has enough cooling capacity to be a viable alternative. The max power used by the thermoelectric prototype was found to be 59.5 Watts producing 170 BTU of heat removal. The thermoelectric prototype needs to produce the same amount of heat removal as an automotive air conditioning system, which is 18,000 BTU, to be a viable option. Scaling the thermoelectric prototype up to use the same amount of wattage as an automotive air conditioning system and get 22,270 BTU of heat removal using 131 units. This means that thermoelectric materials have the capability to produce more heat removal than standard automotive air conditioning systems using the same amount of power.

INTRODUCTION

The theory of this lab is to can calculate the power consumption of the thermoelectric prototype and then compare them to results found in the automotive air conditioning tests. The amount of power used by the thermoelectric prototype can be calculated using Equation 1:

P=IV (1)

I, is the current in amps and V, is volts. P, is calculated in Watts. This equation is used to determine power and is to compare these results with power of an automotive air conditioning system.

PROCEDURE

Material needed:

1. Volt Meter

2. Amp Meter

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3. Thermoelectric prototype

4. Stop watch

Steps:

1. Use the volt meter to measure the Voltage (V) across the Thermoelectric, record data.

2. Use the amp meter to measure the current across each fan, record data.

3. Use the amp meter to measure the current across the thermoelectric material in a time

interval of 3 minutes at 10 second increments.

4. Calculate the high and low values of the current used by the thermoelectric.

5. Calculate the high and low values of the power used by the thermoelectric using Equation 1.

RESULTS

Using the volt meter the voltage across the thermoelectric was 12 V. The current across the two fans was found to be 0.958 amps. The total current was calculated by adding the amps of the two fans to the current of thermoelectric. Table 1 shows the amps measured over a 3 minute time interval.

Table 1 shows the amps measured over a 3 minute time interval using 10 second increments:

seconds amps

0 4

10 3.85

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20 3.78

30 3.74

40 3.7

50 3.67

60 3.65

70 3.64

80 3.62

90 3.61

100 3.6

110 3.59

120 3.59

130 3.58

140 3.58

150 3.58

160 3.57

170 3.57

180 3.57

In Table 1 the amps decrease the longer the thermoelectric is run. This was an unexpected result. It was thought that there would be a constant current across the thermoelectric. The max and min values for current used by the thermoelectric were 4.958 amps and 4.528 amps respectively. Figure 1 shows a graphical solution for how the current decreases over time.

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Figure 1: Graph of amps decreasing over time.

The max power used by the thermoelectric was calculated and found to be 59.49 Watts. At this power consumption, the thermoelectric produces 170 BTU of heat removal. Air conditioning from an idle car using max air condition was measured to be 5,046 Watts. Also, air conditioning from a car moving at 60mph was measure to be 7,806 Watts. When the thermoelectric is scaled to use the same amount of power as a car at idle it would take 85 thermoelectric units and it would produce 14,450 BTU per hour of heat removal. When the thermoelectric is scaled up to use the same amount of power as a car traveling at 60mph it would take 131 thermoelectric units and would produce 22,270 BTU per hour of heat removal. A standard car produces 18,000 BTU per hour of heat removal at maximum capacity.

DISCUSSION

Analyzing the results, the thermoelectric prototype did produce more BTU of heat removal than the car traveling at 60mph but, it failed to produce more BTU of heat removal than the car at idle. This is an interesting analysis just looking at the raw results. With good design that combines all the thermoelectric and uses a single fan that a prototype could be produced that rivals an automotive air conditioning system’s heat removal. Unfortunately, unless the technology advances the thermoelectric will never be able to fit in a car using 85 units or 131 units.

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CONCLUSION

This experiment demonstrates the amount of power the thermoelectric prototype used at maximum cooling capacity. These results will be analyzed and compared to the amount of power an air conditioning system in an automobile uses. The amount of power an automotive air conditioning system uses is much more than the thermoelectric prototype and will need to scale the prototype to the same amount of power in order to find if it has enough cooling capacity to be a viable alternative. The max power used by the thermoelectric prototype was found to be 59.5 Watts producing 170 BTU of heat removal. The thermoelectric prototype needs to produce the same amount of heat removal as an automotive air conditioning system, which is 18,000 BTU per hour, in order to be a viable option. Scaling the thermoelectric prototype up to use the same amount of wattage as an automotive air conditioning system get 22,270 BTU per hour of heat removal using 131 units. This means that thermoelectric materials have the capability to produce more heat removal than standard automotive air conditioning systems using the same amount of power.

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B. Appendix B – Excerpts from Specification Sheets

B.1. Tellurex A22 Unit

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B.2. Tellurex SL1210 Unit

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C. Appendix C – Bill of Materials

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ALTERNATIVE TO COMPRESSOR DEPENDENT AUTOMOTIVE AIR CONDITION

SYSTEMS

CONCURRENCE

Project Team Member – Seth A. Bowman: _____________________ Date:________________

Project Team Member – Stafford C. Camp: _____________________ Date:________________

Project Team Member – Elizabeth A. Clarke: _____________________ Date:________________

Project Team Member – Nicholas M. Tate: _____________________ Date:________________

Project Advisor – Dr. O.H. Griffin: _____________________ Date:________________

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